如何生成嵌套的 ifelse() 语句来评估 R 中混淆矩阵的三个分类二进制级别的预测

How to Produce a Nested ifelse() Statement To Evaluate Predictions For Three Categorical Binary Levels For a Confusion Matrix in R

问题:

我有一个名为 pred_model_Tree1 (three columns; 6 obs; 3 variables) 的预测模型的汇总输出结果,它是从我使用 gbm 方法使用 Caret 和 [=17= 构建的分类器生成的] 包裹。 pred_model_Tree1 是通过使用 test.data (test.data$Country) (见下面的 R 代码).

我想编写一个 nested ifelse() 模型来评估预测,我想使用评估结果从 e1701 pacakge 中的函数 confusionMatrix() 获取汇总统计信息。

我的数据有 nine continuous independent variables,还有一个 dependent variable 叫做 'Country'。这个问题也和我之前问的一个问题有关。我之前遇到过一条错误消息,可以按照我上一个问题中的 link 查看。这是混淆矩阵的输出错误。

Error: `data` and `reference` should be factors with the same levels.

因此,我需要评估模型中的每个预测,使得...

#i.e. if the predicted likelihood that the country is France is '0.9'and the likelihood #it's Holland is '0.1', then the prediction is "France"

#Example
# Evaluate each prediction, i.e. if the predicted likelihood that the country is France is '0.9'
# and the likelihood it's Holland is '0.1', then the prediction is "France"
pred_model_Tree1$evaluation <- ifelse(pred_model_Tree1$France >= 0.5, "France", "Holland")

# Now you can print the confusionMatrix (make sure each factor has the same levels)
confusionMatrix(factor(pred_model_Tree1$evaluation, levels = unique(test.data$Country)),
                factor(test.data$Country, levels = unique(test.data$Country)))

但是,我的 dependent variable 在预测数据 'France'、'Italy' 和 'Spain' 中有 three categorical binary levels。因此,我假设我需要为三二进制评估编写一个 nested ifelse() 语句。

如何应用此逻辑来评估可以进一步用于混淆矩阵的预测,以输出分类器模型准确性的汇总统计信息?我是否还需要使用 >= 大于或等于 0.33 的值,因为有三个级别?我试图按如下方式使用嵌套的 ifelse 函数:

 pred_model_Tree1$evaluation <- ifelse(pred_model_Tree1$France >= 0.5, "France", "Holland",
                                   ifelse(pred_model_Tree1$France >= 0.5, "France", "Spain",
                                   ifelse(pred_model_Tree1$Spain >= 0.5,"Spain", "Holland")))
    
    pred_model_Tree1$evaluation

#The output results only show two countries, not three
1] "France"  "France"  "Holland" "Holland" "Holland" "France" 

预期结果:pred_model_Tree1$evaluation 输出应包含三个国家,在对预测进行评估后重复三次,因此 pred_model_Tree1$evaluation 的级别和结构与pred_model_Tree1 model.

的预测输出
1] "France"  "France"  "Holland" "Holland" "Holland" "France" "Spain" "Spain "Spain"

一如既往,我非常感谢您伸出援助之手。

R-code

#install packages
library(gbm)
library(caret)
library(e1701)

set.seed(45L)

#Produce a new version of the data frame 'Clusters_Dummy' with the rows shuffled
NewClusters=Cluster_Dummy_2[sample(1:nrow(Cluster_Dummy_2)),]

#Produce a dataframe
NewCluster<-as.data.frame(NewClusters)

#Split the training and testing data 70:30
training.parameters <- Cluster_Dummy_2$Country %>% 
createDataPartition(p = 0.7, list = FALSE)
train.data <- NewClusters[training.parameters, ]
test.data <- NewClusters[-training.parameters, ]

dim(train.data)
#259  10

dim(test.data)
#108  10

#Auxiliary function for controlling model fitting
#10 fold cross validation; 10 times
fitControl <- trainControl(## 10-fold CV
                          method = "repeatedcv",
                          number = 10,
                          ## repeated ten times
                          repeats = 10,
                          classProbs = TRUE)
#Fit the model
gbmFit1 <- train(Country ~ ., data=train.data, 
                 method = "gbm", 
                 trControl = fitControl,
                 ## This last option is actually one
                 ## for gbm() that passes through
                 verbose = FALSE)
gbmFit1
summary(gbmFit1)

#Predict the model with the test data
pred_model_Tree1 = predict(gbmFit1, newdata = head(test.data$Country), type = "prob")
pred_model_Tree1

print(pred_model_Tree1)

#Attempt at a nested ifelse() statement

# Evaluate each prediction, i.e. if the predicted likelihood that the country is France is '0.9'
# and the likelihood it's Holland is '0.1', then the prediction is "France"
#>= greater than or equal to
pred_model_Tree1$evaluation <- ifelse(pred_model_Tree1$France >= 0.5, "France", "Holland",
                               ifelse(pred_model_Tree1$France >= 0.5, "France", "Spain",
                               ifelse(pred_model_Tree1$Spain >= 0.5,"Spain", "Holland")))

pred_model_Tree1$evaluation

#The problem is here. The output should contain three countries repeated three times so the levels and structure of the prediction evaluation are the same as the predicted output.

1] "France"  "France"  "Holland" "Holland" "Holland" "France" 

# Now you can print the confusionMatrix (make sure each factor has the same levels)
confusionMatrix(factor(pred_model_Tree1$evaluation, levels = unique(test.data$Country)),
                factor(test.data$Country, levels = unique(test.data$Country)))

数据

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123367978L, 818775L, 123745614L, 25345654L, 3L), Country = c("Holland", 
"Holland", "Holland", "Holland", "Holland", "Holland", "Spain", 
"Spain", "Spain", "Spain", "Spain", "Spain", "Spain", "Spain", 
"Spain", "Spain", "Spain", "Spain", "Holland", "Holland", "Holland", 
"Holland", "Holland", "Holland", "France", "France", "France", 
"France", "France", "France", "France", "France", "France", "France", 
"France", "Spain", "Spain", "Spain", "Spain", "Spain", "Spain", 
"Spain", "Spain", "France", "France", "France", "France", "Holland", 
"Holland", "Holland", "Holland", "Holland", "Holland", "Holland", 
"Holland", "Holland", "Holland", "Holland", "Holland", "Holland", 
"Spain", "Spain", "Spain", "Spain", "Spain", "Spain", "Spain", 
"Holland", "Holland", "Holland", "Holland", "France", "France", 
"France", "France", "France", "France", "France", "Spain", "Spain", 
"Spain", "Spain", "Spain", "Spain", "Spain", "Spain", "Spain", 
"Spain", "Spain", "Spain", "Spain", "Spain", "Spain", "Spain", 
"Spain", "Spain", "France", "France", "France")), row.names = c(NA, 
99L), class = "data.frame")

您可以为每个观测选择预测概率最高的国家:

pred_model_Tree1 = predict(gbmFit1, newdata = test.data, type = "prob")

pred_model_Tree1$evaluation <- names(pred_model_Tree1)[apply(pred_model_Tree1, 1, which.max)]

table(pred_model_Tree1$evaluation)

给出:

 France Holland   Spain 
      1      11      16 

然后 confusionMatrix() 函数使用给定的代码。